1. Field of the Invention
The present invention relates to an electronic keyboard musical instrument having speakers for generating musical sounds disposed at left and right end portions of its housing.
2. Description of Related Art
There have been conventionally known an electronic keyboard musical instrument having speakers for generating musical sounds that are disposed at left and right end portions of its housing. In the musical instrument described in the following Patent Literature 1, for instance, a pair of left and right speakers are provided on the rear of the housing. When acoustic characteristics are considered, it is recognized that there are convexities and concavities in an inside of the housing of the keyboard musical instrument due to a layout of circuit boards and various components, and such convexities and concavities are physical factors that influence acoustic characteristics (decibel value of sound pressure with respect to frequency) of the speakers.
A speaker device according to the following Patent Literature 2 incorporates, in its speaker box, a sound absorbing body formed of a cushioning material in an attempt to improve acoustic characteristics in the speaker box. To approximate the acoustic characteristics to desired ones, the sound absorbing body is formed to have a curved surface shape, and reinforcing members are attached to and interposed in the sound absorbing body to keep the shape of the sound absorbing body. Thus, stable characteristics are maintained.    Patent Literature 1: Japanese Patent 3797164    Patent Literature 2: JP-A-63-217897